Respiratory Tract Infections Flashcards
1
Q
How many droplets does a sneeze produce?
A
40,000
2
Q
How many droplets does coughing produce?
A
3,000
3
Q
What are the most effective vehicles?
A
Dried droplet nuclei
4
Q
Why are dried droplet nuclei such effective vehicles?
A
They stay airborne for long period of time
1-10 micrometres in diameter
5
Q
How long do droplets from Influenza (A and B) persist in the environment?
A
24-72 hours
6
Q
How long do droplets from SAR-CoV-2 persist in the environment?
A
up to 3 days
7
Q
How long do droplets from Bordetella pertussis persist in the environment?
A
3-5 days
8
Q
How long do droplets from Mycobacterium tuberculosis persist in the environment?
A
up to 4 months
9
Q
What is rhinitis?
A
Infection of the nose
10
Q
What is sinusitis?
A
Inflammation of the sinuses often following a common cold infection
11
Q
What is pharyngitis?
A
Infection of the throat
12
Q
What is laryngitis?
A
Infection of voice box
13
Q
What is tracheitis?
A
Infection of trachea
14
Q
What is bronchitis?
A
Infection of bronchi
15
Q
What is bronchioloitis?
A
Infection of bronchioles
16
Q
What is pnemonia?
A
Infection of alveoli
17
Q
What is the first line of defence of the respiratory tract?
A
Mechanisms to remove large incoming particles
18
Q
What are 4 examples of mechanisms that remove large incoming particles?
A
Nasal hairs trap particles
Saliva flushing oropharynx
Mucus production throughout respiratory tract
Mucociliary system in trachea and bronchi
19
Q
What happens to the first line of defence if the epithelial cells are damaged?
A
It won’t work, secondary bacterial infections can occur
20
Q
What can damage epithelial cells of the respiratory tract?
A
bacteria and viruses (e.g. B. pertussis, influenza)
cigarette smoke
pollution
21
Q
What is the immune response in the alveoli?
A
Small particles (0.05-3 micrometres) are phagocytosed by alveolar macrophages
22
Q
What do mucosal secretions produce to provide immune protection?
A
Antimicrobial substances
- lysozyme (lyses bacteria)
- lactoferrin (iron binding protein that deprives bacteria of the free iron needed for growth)
- secretory IgA (targets specific organisms)
23
Q
How are specimens collected from the respiratory tract?
A
Sputum is collected by coughing directly into collection tube or extracted by catheter with suction or during bronchoscopy
Throat or nasopharyngeal swabs
Blood for serological samples
24
Q
What must be avoided when collecting respiratory samples and why?
A
Salvia because it is a contaminant due to containing millions of bacteria.
25
How are respiratory tract infections diagnosed phenotypically?
Through morphology, physiology of organism
- gram stain
- isolation on selective and/or differential media
- biochemical testing: enzyme production, motility, spore formation
- antimicrobial sensitivity
26
How are respiratory tract infections diagnosed immunologically?
Serology: characterising antibodies
- IgM detectable 4-7 days
- IgG detectable 2-4 weeks
Commercial antibody-based kits to detect pathogens
27
How are respiratory tract infections diagnosed genotypically?
PCR presence or absence
qPCR amount of pathogen-specific RNA or DNA
High throughput diagnostic chips
28
Which pathogens adhere to mucosa despite the mucociliary system? (Primary)
Influenza
Rhinovirus
Strep. pneumoniae
M. pneumoniae
29
Which pathogens interfere with the function of cilia? (Primary)
Bordetella pertussis
M. pneumoniae
Strep. pneumoniae
30
Which pathogens resist destruction in alveolar macrophages? (Primary)
Legionella
| M. tuberculosis
31
Which pathogens cause local tissue damage? (Primary)
Corynebacterium diphtheriae
| Strep. pneumoniae
32
What are secondary respiratory pathogens?
They are pathogens that infect the host when the host immune barriers are imparied
33
Which pathogens infect when there is first an initial infection by a respiratory virus?
Staph. aureus
| Strep. pneumoniae
34
Which pathogens infect when there is physiological impairment?
Staph. aureus
| Pseudomonas spp.
35
What disease can cause physiological impairment of the respiratory tract?
Cystic fibrosis
36
Which pathogens can infect when the host has chronic bronchitis?
Strep. pneumoniae
| H. influenzae
37
Which pathogens can infect when the host is immunocompromised?
A. fumigatus
| C. neoformans
38
What is the most deadly lower respiratory tract infection?
Pneumonia
39
What is the most common infection-related cause of death in developing countries?
Pneumonia
40
How many pneumonia deaths per year in children below 5?
935,000
41
What are the causative agents of pneumonia?
Bacteria
Viruses
Fungi
42
How do pathogens reach the lower respiratory tract?
Through deep inhalation of aerosols or aspiration of upper respiratory tract flora
43
What is the main failed defence that leads to pneumonia?
Inhibition of ciliary movement due to tobacco, pollution or prior infection
44
What are the symptoms of pneumonia?
Runny nose, congestion, headache, fever
| Chest pain, cough, production of discoloured sputum, exudate, difficulty breathing
45
What is lobar pneumonia?
Pneumonia in a distinct region or lobe
46
What is bronchopneumonia?
Diffuse infection of the lung
47
What is interstitial pneumonia?
Invasion of the interstitium
48
What is a lung abcess?
Necrotising pneumonia, destruction of the lung parenchyma
49
What are the main causes of community acquired pneumonia?
Viral
Strep. pneumoniae
H. influenzae
50
What are the main causes of nosocomial pneumonia?
Klebsiella pneumoniae
Staph. aureus (MRSA)
Pseudomonas aeruginosa
P. jirovecii
51
What is atypical pneumonia?
Caused from environmental exposure
52
What are 3 examples of atypical pneumonia?
Legionella pneumophilia from cooling towers, environment
Brucella spp. Coxiella burnetti from infected animals
Aspergillus fumigatus, Crytococcus spp. from mulch and animal droppings
53
What percentage of hospitalised patients develop pneumonia?
1%
54
What is nosocomial pneumonia associated with?
Mechanical ventilation
55
What is the mortality rate of nosocomial pneumonia?
30-50%
56
What is the origin of nosocomial pneumonia?
Polymicrobial origin
57
How is nosocomial pneumonia diagnosed?
Microscopic examination and culture of sputum
X-ray
Bronchoscopy, bronchoalveolar lavage, biopsy
58
Which part of the respiratory tract does the common cold infect?
The upper respiratory tract
59
How is the common cold diagnosed?
Through clinical presentation of symptoms
60
What is the most common cause of the common cold?
Rhinoviruses
61
What are the symptoms of the common cold?
Rhinorrhoea
Blocked nose
Sore or scratchy throat
Fever
62
Is there a vaccine for the common cold?
No
63
What are the main 6 viruses that cause the common cold?
```
Rhinoviruses
Coxsackie virus A
Parainfluenza virus
Coronaviruses
Adenoviruses
Echoviruses
```
64
What is the pathogenesis of the common cold?
- Limited virulence mechanisms
- Symptoms associated with the immune response releasing cytokines and inflammatory mediators
- Localised inflammation of nasal mucosa leads to rhinorrhoea
- Can predispose a patient to bacterial secondary infection
65
How is the common cold treated?
rest
fluids
antihistamines
decongestants
66
How is the common cold diagnosed in a lab?
PCR assays
67
What type of virus is Rhinovirus?
Single-stranded RNA virus
| Enterovirus genus
68
How many species of Rhinovirus are there?
3
| A, B and C
69
How many serotypes of Rhinovirus are there?
>165
70
What are the 3 subtypes of Rhinovirus and what cell receptor do they bind to?
Major (M): intracellular adhesion molecule 1 (ICAM-1)
Minor (m): low-density lipoprotein (LDL)
RV-C: CDHR3
71
Why is there such diversity in Rhinoviruses?
Because their RNA-dependent RNA polymerase is error-prone
| It also undergoes recombination with other Rhinovirus species and other species of the genus Enterovirus
72
What are anthroponotic respiratory viruses?
They are viruses that infect chimpanzees in Uganda causing severe respiratory disease
Infecting 56 chimps, killing 5
It is closely related to human rhinovirus C45 strains
73
Chimpanzees are homozygous for what allele?
CDHR3-Y529
74
Is sinusitis often diagnosed?
No
75
What is mild sinusitis usually caused by?
viruses
76
What bacteria can cause sinusitis?
Strep. pneumoniae
| H. influenzae
77
What are the symptoms of sinusitis?
Nasal congestion
Headache
Nasal discharge changes during the course of the illness; may become purulent
78
What percentage of acute sore throats are caused by viruses?
70%
79
What are the 3 main viral causes of acute sore throats?
Adenoviruses
Cytomegaloviruses
Epstein-Barr viruses
80
What are the 2 main bacterial causes of acute sore throats?
Strep. pyogenes
| Strep. pneumoniae
81
What are the symptoms of acute sore throat?
Sore throat
Fever (either low or high grade)
Redness and drainage in the throat
82
Is a laboratory diagnosis required?
No
83
What is acute otitis media?
An infection of the air-filled space behind the eardrum (the middle ear).
84
What demographic is most likely to suffer from acute otitis media?
Young children post cold infection
85
What are the main causes of acute otitis media?
```
Nasopharyngeal residents migrating along eustachian tube
Strep. pneumoniae
H. influenzae
M. catarrhalis
Strep. pyogenes
```
86
What are the symptoms of acute otitis media?
Bulging ear drum
Persistent fluid in the middle ear
Pus
Intense pain
87
What happens if acute otitis media is not treated adequately?
Chronic discharge
| Perforated ear drum
88
How is S. pyogenes diagnose?
From pharyngeal swab
Rapid antigen test - Ab react to outer carbohydrates of group A streptococci
Culture
89
What type of bacteria is S. pyogenes?
gram positive cocci, non-motile, non-sporing
90
Is S. pyogenes fastidious?
Yes, requires sheep blood agar. Shows beta-haemolysis due to haemolysins (streptolysins)
91
Is S. pyogenes catalase positive or negative?
negative
92
Is S. pyogenes sensitive to bacitracin?
yes
93
How is S. pyogenes treated?
Penicillin
94
What disease does S. pyogenes cause?
Strep throat
95
What are the virulence factors or S. pyogenes?
Surface M protein
Hyaluronic acid capsule
Lipoteichoic acid: adhesion to pharynx epithelial cells
Extracellular toxins: streptolysin S and O
96
What encodes pyrogenic exotoxin A (Spe A)?
Lysogenic bacteriophage
97
What disease do lysogenic bacteriophage (Strep A/S. pyogenes) cause?
Scarlet fever
98
What are the symptoms of Scarlet fever?
```
Sore throat
headache
fever
swollen glands in neck
sandpaper-like rash
```
99
What causes Rheumatic fever?
S. pyogenes strains that contain M proteins which are antigenically similar to human cell surface antigens - 'rheumatogenic'
100
What causes damage in rheumatic fever?
Cross-reactive antibodies damage organs
101
What is rheumatic heart disease?
Disease that arises from multiple infections with different M types of S. pyogenes
102
What does rheumatic heart disease cause?
myocarditis and pericarditis in children
| damage to heart valves
103
Is there a vaccine for S. pyogenes?
None that are commercially available
| target conserved region of M protein
104
What does the name Corynebacterium diphtheriae mean?
```
korynee = club for the club shape of the bacterium
diphtheria = leather hide
```
105
What type of bacteria is Corynebacterium diphtheriae?
aerobic, nonencapsulated, non-spore forming, nonmotile, pleomorphic, gram-positive bacilli
106
What disease does C. diphtheriae cause?
Diphtheria
107
What are the symptoms of diphtheria?
```
Severe sore throat
Fever
Malaise
Swollen lymph nodes
Breathing and swallowing problems
Pseudomembrane covers pharynx and tonsils
```
108
What is a pseudomembrane?
It is a covering of dead cells and bacteria
109
What gene does the corynebacteriophage carry?
tox gene which produces an exotoxin
110
How much toxin does 1 corynebacterium produce an hour?
5000 molecules
111
Where does the diphtheria toxin go in the body?
It is released into the bloodstream and leads to complications in organs including the kidneys and heart
112
What is the structure of the diphtheria toxin?
It is a single polypeptide with an A unit and a B unit.
113
What is the cellular process of the diphtheria toxin?
B unit binds to host cell, causing partial cleavage and the toxin-receptor complex in internalised.
The A unit dissociates and moves to the cytosol where it blocks protein synthesis.
114
When was diphtheria first described?
5th century BC by Hippocrates
115
When was the diphtheria antitoxin discovered?
In 1890, Emil von Behring demonstrated serum from animals immunised with C. diphtheriae protected susceptible animals from the diphtheria toxin
116
In what animal is diphtheria antitoxin produced?
Horses
117
How is diphtheria diagnosed?
Culture of nasal and throat swabs on blood agar
| PCR detects toxin producing tox gene
118
How is diphtheria treated?
Antitoxin: contains neutralising antibodies
Antibiotics: penicillins and macrolides
119
Is there a vaccine for diphtheria?
Yes, diphtheria toxoid vaccine
Infanrix hexa: diphtheria, tetanus, pertussis, hep B, polio, H. influenzae type B
DTaP vaccine: Diphtheria, Tetanus, acellular Pertussis
120
What disease does Bordetella pertussis cause?
Whooping cough
121
What is the incubation period of whooping cough?
2-21 days
122
What is the initial catarrhal stage of whooping cough?
1-2 weeks
123
What is the paroxysmal stage of whooping cough?
uncontrollable coughing - "whoops"
| paroxysm: convulsive attack
124
What is the convalescent stage of whooping cough?
recovering from damage to cilia of respiratory tract epithelial cells
125
What are the consequences of whooping cough in infants?
Necrotising bronchitis
| Intra-alveolar haemorrhage
126
What are the 11 virulence factors of Bordetella pertussis?
1. Adhesive structure filamentous haemagglutinin (FHA)
2. Fimbriae 2 & 3 (fim2, fim3)
3. Pertactin (PRN)
4. Tracheal colonisation factor (TCFA)
5. Pertussis toxin (PT)
6. Adenylate cyclase toxin (ACT)
7. Tracheal toxin (TCT)
8. Lipopolysaccharide (LPS)
9. Dermonecrotic toxin (DNT)
10. Serum resistance factor
11. Type III secretion system (TTSS)
127
What does adhesive structure filamentous haemagglutinin do?
Surrounds bacterium like a capsule
| - can also be secreted in soluble form and can act as a bridge between bacterium and the epithelial cell
128
What do fim2 and fim3 do?
adhesion for tracheal epithelial cells
129
What does pertactin do?
adhesion
130
What does tracheal colonisation factor do?
cytotoxin
| adhesion, predominately, in the trachea
131
What does pertussis toxin do?
disrupts cellular processes, increases production of mucus
132
What does adenylate cyclase toxin do?
cytotoxin that inhibits chemotaxis, phagocytosis, bactericidal killing function of neutrophils
133
What does tracheal toxin do?
directly destroys ciliated cells
| Stimulates interleukin-1 causing fever
134
What does lipopolysaccharide do?
leads to the production of a range of cytokines that inhibit defence functions
135
What does dermonecrotic toxin do?
dermal necrosis and vasoconstriction
136
What does serum resistance factor do?
potential adhesins, resistance to complement
137
What does type III secretion system do?
delivers numerous effector proteins from bacterial cytosol directly into host cells, thus hijacking the intracellular machinery of the infected cells
138
In what cell type can B. pertussis replicate?
Macrophages, therefore it can also evade destruction
139
How is whooping cough diagnosed?
Often diagnosed based solely on distinctive symptoms
Culture: nasopharyngeal swab
Serology (IgG or IgA) used after 1 month
PCR
140
How is whooping cough treated?
Macrolide antibiotics most useful in catarrhal phase
141
When is whooping cough most contagious?
In the catarrhal and paroxysmal phases
142
How many cases of whooping cough worldwide in 2014?
24.1 million
143
How many children under 5 died from whooping cough in 2014?
160,700
144
How many cases of whooping cough in Australia per year?
12,000
145
Why is there an increase in cases in Australia over the recent years?
Decrease in immunisation rates
146
Is there a vaccine for whooping cough?
Yes
Whole cell vaccine: killed B. pertussis cells
Acellular vaccine: toxoid, filamentous haemagglutinin, fimbriae
Infanrix hexa
Boostrix: diphtheria, tenanus, pertussis
